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The production of extracellular galactose oxidase is limited to a few fungal species, including the important plant pathogens Fusarium graminearum and F. moniliforme . The best-studied enzyme is the one produced by the mycoparasitic fungus Cladobotryum (Dactylium) dendroides NRRL 2903. The NRRL 2903 strain was first mis-identified as Polyporus circinatus and later re-determined as Dactylium dendroides , although sporulation was never observed and the fungus was regarded as sterile. Upon growth at 25 °C, 50 rpm, in liquid medium containing 2% cellulose as the sole carbon source, and in the presence of 0·5–0·75% yeast extract, conidial production was induced in NRRL 2903, which was re-identified as Fusarium sp. The only other known commercial strain of Cladobotryum (Dactylium) dendroides able to produce galactose oxidase, ATCC 46032, also produced fusiform conidia upon growth in cellulose-containing medium, and was shown to be genetically identical to the NRRL 2903 strain. Genetic comparison with six different representative strains of Cladobotryum dendroides (teleomorph: Hypomyces rosellus ), and four strains of the closely related Hypomyces aurantius , based on the analysis of the presence or absence of a homologous galactose oxidase gene ( gaoA ), RAPD-PCR and RFLP analysis, confirm the distinct nature of the NRRL 2903 strain and Cladobotryum dendroides . Despite the resemblance of NRRL 2903 conidia and conidiophores to those of Fusarium chlamydosporum genetic comparison, with three different strains, suggests NRRL 2903 cannot be re-identified as F. chlamydosporum . Two of the strains, however, contain a region in their genome that is highly homologous to the galactose oxidase gene ( gaoA ), and one strain exhibits extracellular galactose oxidase activity but only partial homology to the gaoA gene of NRRL 2903.

Antagonistic interactions in the form of narrow, black ‘zone-lines’ were observed between paired cultures of elm Phomopsis . Antagonism occurring between the two previously described morphological ‘groups’ of elm Phomopsis was interpreted as inter-specific antagonism, whereas that within each group was intra-specific. Within group one Phomopsis , which had a dimictic mating system, antagonism was very common between isolates from natural populations and between siblings derived from single ascospores. This suggested that several loci were involved. Antagonism was not a sterility barrier and the mating-type locus did not cause vegetative incompatibility. Group two Phomopsis , which was self-fertile, contained a smaller number of v-c types and its siblings intermingled.

Two morphological types of Phomopsis , termed group one and group two, were confirmed as occurring on twigs and bark of elm in Wales, England and Italy. Group one isolates formed abundant conidiomata in culture were culturally heterogeneous and had a dimictic mating system. Group two isolates did not produce conidiomata on agar, were more uniform and self-fertile. No cross-fertilization was detected between the two groups. Three isolates from Italy formed a separate dimictic mating group. Isolates from some other host plants also fell into two groups and some from Fraxinus excelsior, Acer pseudoplatanus and Fagus sylvatica were cross fertile with elm isolates. The taxonomic implications of these results are discussed.

Nectria radicicola is characterized by its distinctive perithecial morphology and anatomy, and by its anamorph, Cylindrocarpon destructans. Several collections readily identified as N. radicicola were made in New Zealand, Indonesia, and Venezuela. Pure cultures derived from ascospores isolated from these collections showed considerable variation in cultural and morphological characteristics. The anamorph, Cylindrocarpon destructans var. destructans, is characterized by a fast growth rate and by the formation of discrete chlamydospores. It is distinguished from C. destructans var. coprosmae (C. Booth) comb. nov., which has a slower growth rate and does not form discrete chlamydospores. Cylindrocarpon destructans var. coprosmae is the anamorph of N. radicicola var. coprosmae (Dingley) stat. nov. Cylindrocarpon macroconidialis sp. nov., the anamorph of N. radicicola var. nuicroconidialis var. nov., is distinguished by larger macroconidia. Other variants of C. destructans are discussed but are not given separate taxonomic status because they are based on single collections. Nectria austroradicicota sp. nov. is distinguished from N. radicicola by having much larger ascospores and by its anamorph, C. auslrodestruclans sp. nov.

First author: Plant Pathology Department, University of Florida, Gainesville 32611-0680; second author: Laboratoire de Recherches sur la Flore Pathogene du Sol, INRA, 17 rue Sully, B.V. 154

Neonectria (Hypocreales: Nectriaceae) species having Cylindrocarpon anamorphs that lack microconidia and chlamydospores include: Neo. discophora var. discophora, Neo. discophora var. rubi, stat nov...